This description relates to TD-SCDMA uplink processing.
Time Division-Synchronous Code Division Multiple Access (TD-SCDMA) is a newly emerging third generation wireless standard widely expected to be deployed in China. TD-SCDMA is also part of 3rd Generation Partnership Project (3GPP) wireless standards. 3GPP is a global collaboration formed of numerous telecommunications associations whose mission is to assist in the creation and implementation of a 3G telecommunication system specification that is globally applicable, making TD-SCDMA an important standard for 3G applications.
TD-SCDMA is based on spread spectrum technology and combines aspects of both time division multiple access (TDMA) and code division multiple access (CDMA) concepts. One departure of TD-SCDMA from other 3G standards (e.g., Wideband Code Division Multiple Access (W-CDMA)) is the use of time division duplex (TDD) instead of frequency division duplex (FDD). Amongst other things, TDD separates outward and return signals to emulate full duplex communication over a half duplex communication link. TDD has a strong advantage over FDD in situations in which there is an asymmetry in the uplink and downlink data speed. Uplink refers to the data communications in a direction from the mobile device to the base station, whereas downlink refers to data communication in a direction from the base station to the mobile device.
In some communications, the uplink and downlink portions may have very different speed and bandwidth requirements. For example, when a mobile telephone downloads information from a network, downlink processing may require significantly more of the channel bandwidth than uplink processing. Similarly, when the mobile device uploads information to the network, uplink processing may require significantly more of the bandwidth. By dynamically adjusting the number of time slots used for downlink and uplink processing, the system can more easily accommodate asymmetric traffic with different data rate requirements on downlink and uplink than FDD schemes are capable. For example, as the amount of uplink data increases, more bandwidth can dynamically be allocated to the uplink processing.
As discussed above, TD-SCDMA uses both TDMA and CDMA concepts. The synchronous aspect of the TD-SCDMA standard means that uplink signals are synchronized at the base station receiver, achieved by continuous timing adjustments.